Botany

Anatomy of a Plant Seed



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Inside each seed there is an embryonic plant. A seed contains the next generation of the plant it comes from and, as such, the plant goes to great lengths to ensure the survival of the seed.

Every seed is different and some are large, some small. Some have adaptations to enable them to survive long journeys by sea whilst others need to germinate almost as soon as they fall to remain viable. Whatever the adaptation a seed has similar basic anatomy.

First there is the endosperm. This feeds the developing embryo and also provides nutrition to the germinating plant. It takes a lot of energy for new growth on germination and so the endosperm provides a rich source of proteins and fats. The embryonc leaves are called the cotyledons (developing from the hypocotyl) and these are identifying characteristics with monocotyledons having one seed leaf and dicotyledons possessing two. The cotyledons always grow toward light and will turn green almost as soon as they emerge so they can begin the process of manufacturing food for the plant.

As well as the embryonic leaves, there is the radicle which always grows towards gravity and becomes the root of the seedling.

Surrounding the seed is the seed coat or testa. This protects the seed from water, cold and often is thick enough to allow the seed to be dispersed by passing through the gut of an animal or bird with no harm being done to the contents.The testa contains tiny pores which allow water in for germination. These pores may initially be blocked by chemicals which prevent germination.These are slowly washed away until the pores are open and this helps temperate climate seeds to germinate only after a period of cold and wet (winter).Some seed coats have chemicals which are only taken away br burning, such as in bush fires or forest fires. This ensures they germinate into the fesh, fertile ash andget a head start on rival plants.

Seeds often require a period of cold before germination and we mimic this using stratification by placing them for a period in a cold place like a fridge.This tricks the plant into thinking it has had a winter and so iterates as soon as it is taken to a warmer environment.

So, contained in the largest and tiniest seed is the embryonic next generation of that plant. Seeds are precious and plants go to great lengths to ensure their seeds can survive.

Of course, seeds also contain the genetic information a plant needs so it grows to be the species it has been bred from, or a hybrid if the cross has been between two related parents. It s this perhaps which makes seeds most special. Many plants can reproduce assexually but the offspring will be clones of the parents.

Seed production means the embryonic plant has genetic information from two parents and so adaptations can occur through anomalies which survive, enabling plants to do what they do best - grow and adapt to our ever changing environment.



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